In connection with orthopedic surgery, different kinds of implant are often used. It is then a matter of fixing the implant to different kinds of bones by means of bone screws which are screwed to the bone through corresponding holes in the implant, and/or locking or fixing different implant parts to each other by means of different types of conventional locking screws which are screwed into one part to be lockingly engaged with the other part.
When using bone screws, it is well known, for locking thereof relative to the implant that is fixed by means of the bone screws, to use special locking screws which are screwed into the slit end or head or main part of the respective bone screws so as to expand the end or main part into locking engagement with the surrounding wall of the implant hole. For the purpose of achieving the necessary expansion there are arranged coacting conical surfaces on the locking and bone screws, the coacting surfaces of which, during axial relative displacement therebetween, cause a radially outwardly directed effect on said end or main part.
Typical constructions of this type are described in e.g. U.S. Pat. No. 4,484,570 and WP 88/03781.